Internal feedback electric discharge device



Oct. 11, 1966 D. w. HAWKINS INTERNAL FEEDBACK ELECTRIC DISCHARGE DEVICE Filed July 16, 1962 FIG.|.

Ill-IA ill llllll I I1 I llll knnu 1. I I

lNVENTORZ DARYL w. HAWKINS,

IS ATTQRNEY- United States Patent f 3,278,788 INTERNAL FEEDBACK ELECTRIC DISCHARGE DEVICE Daryl W. Hawkins, Ballston Lake, N.Y., assignor to Generai Electric Company, a corporation of New York Filed duty 16, 1962, fier. No. 210,065 5 (Ilairns. (Cl. 313250) My invention relates to electric discharge devices and pertains more particularly to a new and improved ultra high frequency oscillator tube including new and improved means providing internal feedback capacitance coupling between the cathode and anode of the tube.

It is well known in the art that in a grounded grid U.H.F. oscillator circuit operating efficiency and power output can be enhanced by providing a feedback voltage of the proper phase and magnitude between the cathode and anode of the oscillator tube in the circuit. When conventional triodes or tetrodes are employed in oscillator circuits, the mentioned feedback usually requires some form of external feedback circuitry. Such external feedback circuitry usually complicates the overall circuit design and tends to result in limited frequency range and a need for critical adjustments of the circuit. Consequently, efforts have heretofore been made to provide tubes including means effective for providing internal feedback occurring intern-ally of the tube envelope. Such a tube usually incorporates a probe-like element extending in the tube envelope from the cathode toward the anode for effecting an internal feedback capacitance in the tube. See US. Patent 2,423,819 for example. However, in such an arrangement the probe-like element constitutes a cathode extension subject to heat losses which can adversely affect the thermal efficiency of the cathode. Additionally, the probe-like element extends the cantilever of the cathode mount and thus tends to subject the cathode to greater movements during operation under vibratory conditions as in a moving vehicle. This can have the undesirable eifect of varying the capacitances between the several electrodes and thus limiting the operating stability of the tube. Still further, a simple probe-like element generally does not present a substantial surface area to the cooperating electrode and thus is not effective for providing the degree of coupling required. In the prior art this situation has resulted in the provision on the probe of ball-shaped and diskishaped elements to increase the capacitive coupling to the adjacent anode. These elements serve to increase the coupling but unfortunately also increase the heat losses from the cathode and the tendency toward increased vibratory movements and the resultant undesirable effects thereof discussed above.

My invention contemplates the provision of a new and improved U.H.F oscillator tube incorporating means whereby a desired internal feedback capacitance coupling is provided between the cathode and anode of the tube without the use of cathode extensions or any other constructions which can adversely affect the thermal efficiency of the cathode. Additionally, my invention contemplates an internal feedback arrangement which is devoid of any elements which are either themselves subject to vibratory motions or can increase the tendency of vibratory motions of other elements in the tube. Further, my invention contemplates an internal feedback arrangement which is effec tive for affording a substantial controlled degree of feedback capacitance coupling without introducing undesirable side electrical etfects such as variations in interelectrode capacitances and instability. Still further, and according to my invention, a desired internal feedback capacitance is obtainable simply with the use of an improved anode construction.

Accordingly, a primary object of my invention is to provide a new and improved U.H.F. oscillator tube.

Patented Oct. 11, 1956 "ice Another object of my invention is to provide a new and improved U.H.F. oscillator tube incorporating new and improved means for providing internal feedback capacitance coupling between the cathode and anode of the tube.

Another object of my invention is to provide a new and improved U.H.F. oscillator tube incorporating new and improved means for providing internal feedback capacitance coupling between the cathode and anode of the device without adversely aifecting the thermal efficiency of the cathode and without introducing undesirable side electrical effects.

Another object of my invention is to provide in a U.H.F. oscillator tube new and improved means which is effective for providing internal feedback capacitance coupling and yet is relatively simple in construction and can be constructed without any increase in the number of parts required in constructing the tube without an internal feedback arrangement.

Another object of my invention is to provide a new and improved electric discharge device incorporating a new and improved anode construction.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide an electric discharge device of the U.H.F. oscillator tube type which comprises a coaxial arrangement of generally tubular electrodes including a cathode, at least one grid and an anode. The cathode is of the indirectly heated type and includes a cup-shaped cathode member having a cylindrical ernissive surface and a substantially planar non-ernissive end. The grid surrounds the cathode and has an open end through which the non-emissive end of the cathode is exposed or non-shielded in respect to the opposed surface of the anode. Fitted over the cathode and grid in nesting relationship is a cup-shaped anode which comprises a wall section of the tube envelope and includes a cylindrical active surface and a closed end wall. Extending inwardly from the closed end Wall of the anode and spaced a predetermined distance from the non-emissive end of the cup-shaped cathode member is a conductive projection. The projection and the cathode cooperate in providing internal feedback capacitance coupling between the cathode and anode. The conductive projection can advantageously comprise an exhaust tubulation located coaxially in the anode member and having the inner end thereof extending into the anode member a predetermined distance toward the cathode end. The use of a tubulation can also facilitate adjustment of the spacing between the cathode and projection. If desired, a getter arrangement including a substantially planar getter element can be mounted on the end of the cathode in which case the projection extends a predetermined distance relative to the planar getter element. Externally of the tube envelope, and provided in order to prevent damage to the tubulation and to preserve the predetermined spacing of the inner end of the tubulation and cathode, I provide an improved taubulation-protecting cover and means for securing same to the device. Additionally, if desired, the tubulation can be replaced by a coaxial cylindrical boss formed integrally on the internal surface of the end wall of the anode and projecting toward the cathode for cooperating therewith to provide the mentioned international feedback capacitance coupling between the anode and cathode.

For a better understanding of my invention, reference may be had to the accompanying drawing in which:

FIGURE 1 is an enlarged partially sectionalized view of an electric discharge device constructed according to one embodiment of my invention; and

3 FIGURE 2 is an enlarged fragmentary sectional view illustrating a modified form of my invention.

Referring to the drawing, there is shown in FIGURE 1 a ceramic and metal triode of the type adapted for use as an oscillator tube and including a stacked arrangement of alternate ceramic and metal members defining an evacuated envelope generally designated 1.

The envelope 1 comprises a plurality of mutually insulated coaxial contacts including an anode contact 2, a grid contact 3 and a cathode contact 4, which cathode contact serves also as one contact for a heater circuit, and another heater contact 5. A cylindrical insulator 6 is hermetically sealed between and separates the anode contact 2 and the grid contact 3, a smaller diameter cylindrical insulator 7 is appropriately hermetically sealed between the grid contact 3 and the cathode contact 4,

and a still smaller diameter cylindrical insulator (not shown) is hermetically sealed between and mutually electrically isolates the cathode contact 4 and the heater contact 5. The envelope 1 further includes an inverted cupshaped anode block or member 10 which has an outer flange 11 formed thereon and hermetically sealed in a rim 12 on the anode contact 2. The anode member 10 constitutes the upper end wall section of the envelope 1 and will be described in greater detail hereinafter.

The enveloper 1 contains coaxial cooperating cathode and grid assemblies generally designated 13 and 14 respectively, and which are each suitably supported from and electrically connected to appropriate ones of the ex ternal coaxial contacts. Specifically, the cathode contact 4 includes a cylindrical internal extension 15 on the upper end of which is mounted the cathode assembly 13. The cathode assembly 13 includes an inverted cup-shaped cathode member 16 having the rim thereof suitably secured, as by spot welding, to the upper end of the cylindrical extension 15. The cathode member, 16 also includes a cylindrical surface 17 and a closed planar bottom or transverse end wall 18. The cylindrical surface 17 is adapted for being rendered emissive when heated, as by carrying a suitable emissive oxide coating; and provided in the member 16 for heating same is a heating element 20. The heating element 20 comprises a suitable coiled filament 21 having one end afiixed to a conductive center support rod 22. The support rod 22 and the other end of the filament 21 extend through suitable apertures in a disk-shaped insulator 23 affixed transversely in the upper endof the cylindrical cathode contact extension 15. The lower end of the support rod 22 is conductively secured, and thus electrically connected, to the inner surface of the extension 15. The mentioned other end of the filament is spot welded to a rod-like lead 24 which is conductively connected to the heater contact 5. Thus, an electrical connection to the cathode member 17 can be made through the cathode contact '4, and a heater circuit can be completed through the cathode contact 4 and the heater contact 5.

, Mounted on the bottom or end: wall 18 of the cathode member 16 is a getter supporting arrangement generally designated 25. This arrangement includes a disk-like getter element 26 afiixed to a disk-like support member '27 including a plurality of radially expansible generally U-shaped mounting elements 28 having the outer ends thereof joined to the bottom 18 of the cathode member.

This supporting arrangement does not specifically constitute part of the present invention but is disclosed and claimed in my copending application S.N. 30,154, filed May 19, 1960 now U.S. Patent 3,082,346 and assigned to the same assignee as the present invention. However, in the present invention, and in a manner to be described hereinafter, the closed end of the cathode assembly 13 cooperates with the anode 10' in affording the desired in ternal feedback capacitance coupling and this closed end can comprise either the substantially planar bottom 18 of the cup-shaped member 16 or any substantially planar element mounted thereon and at cathode potential, such as the disk-shaped getter element 26 supported on the end of the cathode member.

The grid assembly 14 comprises a cylindrical array of grid wires 30 mounted on a cylindrical support 31 which is conductively connected to the grid contact 3. The upper end of the grid assembly 14 is open or unobstructi-ng so as to expose, or be electrically non-shielding in respect to, the closed end of the cathode assembly 13. Thus, the grid assembly does not detract from the capability of the cathode member in cooperating with the anode to provide the mentioned internal feedback capacitance coupling therebetween.

The anode block or member 10, which can advantageously be formed of copper, includes a cylindrical active inner surface 32 adapted for cooperating with the cathode emissive surface 17 and the grid 14 in the usual manner. The anode block 10 also includes a transverse end wall 33 extending parallel to the closed end of the cathode assembly. Projecting coaxially through the 'end wall 33 of the anode and extending therein a predetermined distance toward the closed end of the cathode assembly is a conductive tubular element or tubulation 34. The tubulation 34 serves several purposes. First, in a well-known manner it is adapted for enabling exhaust therethrough of the tube envelope. Secondly, it cooperates with the closed end of the cathode assembly for providing the above-mentioned desired internal feedback capacitance coupling whereby the tube is adapted for improved operating efficiency and power output without the reliance upon external feedback circuitry which can be complicated, and which tends to limit frequency range and requires critical adjustments. More specifically, the inwardly projecting end of the tubulation 34 includes a transverse end extending parallel and in predetermined spaced relation to the disk-like getter element 26 which is exposed through or is nonshielded by the end of the grid assembly 14 and which is at cathode potential and comprises part of the closed end of the cathode assembly 13. Thus, the cathode and anode are capacitance-coupled for providing the mentioned internal feedback coupling therebetween.

The tubulation 34 is adapted for being pinched off in the manner indicated at 35 after exhaust of the tube envelope 1. However, prior to exhaust, means can be extended through the tubulation for adjusting the oathode assembly relative to the tubulation both in respect to axial spacing and coaxial alignment. Additionally, in

order to protect both the tubulation pinch-off 35 and to Y avoid disturbance of the predetermined adjustment of the spacing between the anode projection and cathode assembly, I have provided a cup-like tube shield or cover 36 securely positioned over the exposed end of the tubulation. In the illustrated arrangement the anode assembly is provided with a metal annulus 37 suitably secured to the top of the anode block 10 about the tubulation 34 and including a shoulder 38 which can be provided by forming the annulus 37 with an annular recess as shown or any other cross sectional configuration, such as an inwardly downwardly inclined frusto-conical surface, which will provide a suitable outwardly extending shoulder 38 on the side closest the outer end of the tubulation. The rim of the cover 36 is secured to the anode block by at least one, and preferably a circumferentially spaced plurality of, indentations or inwardly bent sec tions 39 engaging the member 37 under the shoulder 38.

Illustrated in FIGURE 2 is a modified form of my invention including means other than a tubulation for providing an inward projection on the inner surface of the anode for cooperating with the closed end of the cathode assembly to provide the desired internal feedback capacitance coupling between these elements. In this form of my invention the cathode assembly 13 and grid assembly 14 can be essentially identical in structure and purpose to those illustrated in FIGURE 1 and are designated by the same numerals. However, in this embodiment, the bottom or closed end of the cathode member 16 is not provided with a getter assembly. As indicated above, the getter assembly is not essential to the present invention but can be included and can constitute part of the closed end of the cathode assembly if it is at cathode potential and presents a substantially planar surface to the anode for cooperating therewith to provide the desired capacitance feedback coupling of cathode and anode.

The anode assembly of the second embodiment which is generally designated 40 in FIGURE 2 also comprises a cup-shaped block of conductive material, which can also be advantageously of copper and is formed to include a cylindrical active surface 41 and a transverse end Wall 42. However, the anode 40 does not carry a tubulation, other means (not shown) being provided to effect exhaust of the tube envelope. Instead of relying upon a tubulation to provide an inwardly extending element to cooperate with the cathode, the present embodiment includes a cylindrical inward projection or boss 43 formed integral with and off the transverse end wall 42. The boss 43 is coaxial with the cathode and grid assemblies and includes a planar inner surface 44 which extends parallel and in predetermined spaced relation to the end surface 18 of the cathode member 16. These opposed parallel anode and cathode surfaces cooperate in eifecting an internal feedback capacitance coupling between the anode and cathode for the same purpose as the internal feedback structure provided in the abovedescribed first embodiment. The remainder of the device illustrated in FIGURE 2, namely, the various electrode supports, envelope wall elements and coaxial contacts can he identical to those illustrated in FIGURE 1.

It will be seen from the foregoing that I have provided an improved oscillator tube including an internal feedback arrangement which is not subject to the shortcomings of previous internal feedback constructions. Specifically, my feedback construction does not involve the use of cathode extensions, probes or any other parts which could result in heat losses and could adversely affect the thermal efficiency of the cathode assembly. Additionally, the opposed cooperating electrode surfaces whereby the capacitance coupling is eifected are substantially rigidly mounted and thus are adapted for operating under substantial vibratory conditions without being subject to relative movements which could cause variations in the capacitances therebetween and result in undesirable electrical eifects. Also, the opposed coupling surfaces can be substantial in area and the desired coupling can be attained simply by adjusting predeterminedly the spacing therebetween. Still further, it is to be noted that in accordance with my invention the internal feedback is obtainable without the addition of parts but can be attained simply by utilizing one of the previously used elements, namely, the exhaust tubulation for the additional purpose of cooperating with the cathode to effect a feedback capacitance coupling. Also, in the case of the embodiment of FIGURE 2 no additional parts are required, the desired effect being obtainable simply by forming the anode block to include the inwardly projecting boss 43 extending coaxially on the inner end thereof. Still further, it will be seen from the foregoing that my invention is also applicable where it is desired to mount a parasitic getter structure on the closed end of the cathode assembly and the presence of the mentioned getter assembly does not adversely affect the operation of my invention provided the getter structure includes a planar element at cathode potential and opposes the inwardly extending projection on the anode assembly. It is to be understood from the foregoing that the desired feedback is provided by cooperation of the opposed surfaces on the ends of the cathode assemblies and inward projections on the anodes. In the disclosed structures these opposed end surfaces are substantially planar. However, it is to be understood that other than planar surfaces can be employed in providing the desired capacitance coupling. For example, opposed, conforming and cooperating hemispherical surfaces can be employed, if desired, in providing the required capacitance coupling.

While I have shown and described specific embodiments of my invention, I do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A grounded grid electric discharge device comprising a cathode, at least one grid and an anode arranged in coaxial cooperating relation, said anode comprising a tubular member having a closed end, said cathode comprising a tubular member having a closed end and positioned within said anode so that said closed ends are in adjacent pre-detennined spaced relationship, an inward projection on said anode extending toward said closed end of said cathode and cooperating therewith, to provide an internal feedback capacitance coupling between said cathode and anode, and said grid having a substantially unobstructed electrically non-shielding opening surrounding said spaced apart opposed ends to effect capacitive coupling between said cathode and said anode projection, said opposed ends which provide said capacitance coupling being out of the electron emitting and controlling area of said anode and cathode, said closed end of said cathode comprising a substantially planar section and said inward projection on said anode comprising a cylindrical member including a transverse end surface extending parallel and in predetermined spaced relation to said planar section of said cathode.

2. A grounded grid electric discharge device comprising an envelope including a closed end cup-shaped anode element constituting an envelope section, a closed end cathode and at least one grid mounted in coaxial nesting relation in said anode so that closed ends are in adjacent predetermined spaced apart relationship, said grid having a substantially unobstructed opened end surrounding the said space between said spaced apart closed ends to minimize shielding of said closed end of said cathode from the end wall of said anode, said closed end wall of said anode having an inwardly extending projection closely spaced from and cooperating with said closed end of said cup-shaped cathode member to provide an internal feedback capacitance coupling between said cathode and anode, the said projection and the said closed end of said cathode which provide said capacitance coupling being out of the thermionic emitting and controlling area of said anode and said cathode.

3. A grounded grid ultra high frequency electric discharge device comprising an envelope including a cupshaped anode element constituting a wall section of said envelope, a cathode and at least one grid mounted in coaxial cooperating relation in said anode, said cathode comprising a cup-shaped member having a closed substantially planar end section nesting within and closely spaced in predetermined relation to said anode, the nesting relationship of said anode and said cathode providing active anode and cathode cylindrical surfaces in the operation of said device, and a conductive tubular exhaust element sealed coaxially through the end wall of said anode with the inner end of said tubulation projecting a predetermined distance inwardly in said anode in predetermined spaced relationship to said closed end section of said cathode to provide an internal feedback capacitance coupling between said cathode and anode, said grid being open ended to surround the space between said projection and said cathode to minimize shielding of said closed end section of said cathode from the end wall of said anode, the inner end of said tubulation and the opposed closed end section of said cathode which provide the said feedback capacitance coupling being out of the thermionic electron emitting and controlling area of said anode and said cathode, and an annular member. secured about the outer end of said tubulation and providing an outwardly extending shoulder immediately adjacent said anode, and a cup-like element fitting over the outer end of said tubulation to protect same and having at least portions of the rim thereof extending under said shoulder to retain said cup-like element in position over said tubulat-ion.

4. A grounded grid electric discharge device comprising an envelope, a cup-shaped anode element constituting a wall section of said envelope, at cup-shaped cathode and at least one surrounding grid mounted in coaxial operating nesting relation andprojecting into said anode, said cathode having a closed substantially planar end section spaced closely adjacent to said anode, said grid having an unobstructed open end surrounding the space between said cathode and said anode and effective to minimize shielding of said closed end section of said cathode from the end wall of said anode, and a cylindrical boss formed integrally and coaxially on the inner surface of the end wall of the said anode projecting a predetermined distance inwardly in said anode toward said closed planar end section of said cathode and cooperating therewith to provide an internal feedback capacitance coupling between said cathode and anode, the said cylindrical boss and the said closed planar end section which provide said feedback capacitance coupling being out of the thermionic electron emitting and controlling area of said anode and said cathode.

5. A grounded grid electric discharge device comprising a cathode, at least one grid and an anode arranged in coaxial cooperating relation, said cathode comprising a cylindrical member having a getter arrangement including a getter element mounted transversely on the end of said cathode and adapted for assuming cathode potential, said anode comprising a cup-shaped element having a transverse end wall including an inward projection cooperating with said getter element to provide-an internal feedback capacitance coupling between said cathode andanode, a substantially unobstructed grid having an-open end and surrounding said cathode and anode to provide capacitive coupling between said getter element and anode projection, the said inward projection and said getter element which provide said capacitance coupling being out of the thermionic electron emitting and controlling area of said anode and said cathode, said getter element comprising a substantially planar disk and said inward projection comprising a cylindrical member having a substantially planar transverse end surface extending in parallel predetermined spaced relation to said disk.

References Cited by the Examiner UNITED STATES PATENTS 1,884,591 10/1932 Davis 315-59 2,167,852 8/1939 Rose 313-174 r 2,190,668 2/1940 Llewellyn 315-41 X 2,402,602 6/1946 Chevigny 313-326 X 2,412,998 12/1946 Litton 313-326 X 2,451,249 10/1948 Smith et al 315-41 X r 2,556,855 6/1951 Stutsman 313-326 X 2,562,820 7/1951 Reid 315-57 X 2,712,096 6/1955 McKenzie 315-58 2,768,329 10/1956 Smith 315-58 2,803,749 8/1957 Andrews 315-58 X 2,806,166 9/1957 Bennett et al. 313-174 2,898,501 8/1959 Wadia et al. 313-174 3,022,440 2/ 1962 Soileau 315-250 3,084,274 4/1963 Krey 313-313 X JOHN W. HUCKERT, Primary Examiner.

C. E. PUGH, J. D. KALLAM, A. J. JAMES,

, Assistant Examiners. 

1. A GROUNDED GRID ELECTRIC DISCHARGE DEVICE COMPRISING A CATHODE, AT LEAST ONE GRID AND AN ANODE ARRANGED IN COAXIAL COOPERATING RELATION, SAID ANODE COMPRISING A TUBULAR MEMBER HAVING A CLOSED END, SAID CATHODE COMPRISING A TUBULAR MEMBER HAVING A CLOSED END AND POSITIONED WITHIN SAID ANODE SO THAT SAID CLOSED ENDS ARE IN ADJACENT PRE-DETERMINED SPACED RELATIONSHIP, AN INWARD PROJECTION ON SAID ANODE EXTENDING TOWARD SAID CLOSED END OF SAID CATHODE AND COOPERATING THEREWITH, TO PROVIDE AN INTERNAL FEEDBACK CAPACITANCE COUPLING BETWEEN SAID CATHODE AND ANODE, AND SAID GRID HAVING A SUBSTANTIALLY UBOBSTRUCTED ELECTRICALLY NON-SHIELDING OPENING SURROUNDING SAID SPACED APART OPPOSED ENDS TO EFFECT CAPACITIVE COUPLING BETWEEN SAID CATHODE AND SAID ANODE PROJECTION, SAID OPPOSED ENDS WHICH PROVIDE SAID CAPACITANCE COUPLING BEING OUT OF THE ELECTRON EMITTING AND CONTROLLING AREA OF SAID ANODE AND CATHODE, SAID CLOSED END OF SAID CATHODE COMPRISING A SUBSTANTIALLY PLANAR SECTION AND SAID INWARD PROJECTION ON SAID ANODE COMPRISING A CYLINDRICAL MEMBER INCLUDING A TRANSVERSE END SURFACE EXTENDING PARALLEL AND IN PREDETERMINED SPACED RELATION TO SAID PLANAR SECTION OF SAID CATHODE. 